The present disclosure relates generally to turbomachinery, and, more specifically, to methods and systems for controlling outflow leakage in compressor stages within gas turbines.
In at least some known gas turbines, ambient air is channeled into a compressor section of the gas turbine via an air intake. The compressor section compresses the air prior to channeling the air via a main air flowpath to a combustor section for ignition with a fuel. In at least some known gas turbines, compressed air present within higher tier compressor stages (i.e., further downstream stages) can be prompted to leak out of the main air flowpath, via cavities present within an inner wheelspace of the compressor section. Such cavities are oriented radially inward of the main flowpath of the air being compressed. More particularly, compressed air within the higher compressor stages is prompted to move upstream, into cavities defined on upstream and downstream sides of adjacent rotor wheels that are located in upstream, lower tier compressor stages. Specifically, these cavities receiving the leakage air are located between adjacent rotor and spacer wheels. The air pressure within these cavities is increased, resulting in the leakage of air back out into the main air flowpath in the lower tier compressor stages, where the leakage air can disturb the flow of air around the airfoils in the lower tier compressor stages.
In at least some known gas turbines, forward leakage of air can create conditions in which the gas turbine may experience an increased susceptibility to stall. Elevated ambient air temperatures can further increase the susceptibility of a gas turbine to compressor stall. In order to address such leakage on hot days, the gas turbine may have to be operated at a speed that is lower than its rated speed, to prevent the occurrence of compressor stall.